Reference may be had to U.S. Pat. Nos. 4,624,098 and 4,295,320, incorporated by reference herein, for a description of conventional type capping machines because the details of such machines will not be described in detail in this specification. Generally speaking, the capping machine or conventional capping apparatus includes a rotatable star wheel machanism having a plurality of capper pockets adapted to receive bottles fed in an assembly line fashion thereto. Overlying the capper star wheel is a turret capper head which rotates in synchronism with the capper star wheel. Each capper head employs a clutch mechanism whereby the head is rotated and driven axially downward at a predetermined force and torque limiting value to tighten the caps onto the bottle neck. an infeed star mechanism is mated to the capper star mechanism to feed filled bottles to an entry point at the capper star wheel and an outfeed rotable star mechanism is similarly mated to the capper star mechanism to transfer the capped bottles from an exit point at the capper star wheel. A stationary rear guide extending generally between the entry and exit points is spaced radially outwardly from the capper pockets of the capper star wheel and functions to retain the bottles in the pockets as the capper star wheel rotates. This is the conventional capper mechanism employed in bottling plants today and it is the mechanism to which the present invention relates.
With respect to the cap or the closure itself, for years, the crown was the dominant closure employed and is still in use today in the beer industry. The crown closure eventually was replaced by caps or closures commonly called "roll-on" caps. This type of closure comprised a cap shell of aluminum which was inserted over the threaded neck of the container and then secured in place by rolling threads in situ into the walls of the cap shell. Capper heads which performed the rolling operation typically exerted downward forces of 500 pounds onto the neck of the bottle. This force, of course, was transmitted to the base of the bottle and thereat developed a sufficient frictional force with the capper star wheel base to prevent bottle rotation within the pocket of the capper star wheel.
The roll-on cap, in turn, has been replaced with plastic or metal locking type, threaded caps. In the beverage industry, threaded safety caps have a frangible connection at the cap base thereof which will herein be referred to as a "lock band". In the case of a metal cap, the capper heads simply crimped the lock band about the bottle neck portion beneath the lowermost thread. In the case of a plastic cap, heat was applied to the lock band of the cap after the cap was tightened onto the filled container and shrunken, in a somewhat frangible manner, to the neck of the bottle. Plastic caps with heated lock bands can be applied to either plastic or glass bottles. In the plastic cap application, the force of the capper head reduced to a downward thrust of about 50-60 pounds. This force was not sufficient to generate a sufficient frictional force at the base of the bottle to prevent the bottle from rotating in the pocket of the capper star wheel. Bottle rotation in the capper pocket prevents adequate cap tightening.
Accordingly, several different concepts have been employed to prevent bottle rotation for plastic cap applications. For example, the bottle was shaped with a wedge sidewall configuration and the transfer mechanisms between the various star wheels modified to feed the bottles into configured pockets. Additionally, a high friction material such as polystyrene was applied to the bottom of the bottle, especially for glass bottles, so as to better grip the base of the capper star wheel and enhance the frictional, anti-rotation force. Such modifications, while functional, were not acceptable. The consuming public did not accept configured bottles. Adding friction material to the bottle materially increased its cost and its effectiveness was diminished in the event the base of the capper star wheel became wet or was subjected to oil, both of which are common occurrences in the operation of a bottling plant. U.S. Pat. No. 4,624,098 to Trendel proposed an acceptable solution. In Trendel, a belt subtends a portion of the pocket to urge the bottle against the rear guide thus increasing the friction between the side of the bottle and the rear guide which, when added to the frictional force at the base of the bottle, prevented bottle rotation during tightening of the cap. This has proven acceptable in capping applications where the downward force exerted on the bottle head from the capping head is as low as 50-60 pounds.
More recently, plastic, threaded safety caps or closures have been developed which do not require the application of heat to set or position the lock band. By tapering the bottle neck beneath the lowermost thread and also tapering the edge of the lock band, the lock band simply snaps in a locking position vis-a-vis the tapered fit when the cap is tightened to a predetermined position. This position occurs when the axial downward face on the cap from the capper head is about 15-20 pounds. This low capper heat axial force makes retention of the bottle within the pocket very difficult, even with the use of very strong elastic bands in the pocket such as disclosed in the '098 patent. Accordingly, the device now in conventional use for such threaded plastic caps, at least when used on plastic bottles typically of the 1-2 liter size, is a anit-rotation device developed by Metal Box p.l.c. This device is shown in FIGS. 8 and 9 whereat a bottle 10 having a threaded neck portion 11 is received in a peripherally formed capper pocket 13 of capper star wheel 14 at a position below its threaded end. The neck 11 is conventionally forced into pocket 13 by a stationary, smooth rear guide 16. Capper pocket 13 has an arbitrarily designated forward converging surface 18 and a rearward converging surface 19. Forward converging surface 18 has backwardly facing teeth which oppose the tightening direction of rotation, indicated by arrow 20, of the capper head. Rearward converging surface 19 is smooth and acts, in conjunction with rear guide 16, as a cam surface to drive the bottle neck against the teeth of forward converging surface 18. As shown in FIGS. 8 and 9, the backwardly facing teeth of forward converging surface 18 are adjustably mounted by means of a slotted tab 21 which is precisely adjusted in relationship to the diameter of neck portion 11 to permit neck 11 to enter pocket 13 while resisting rotation of neck 11 during cap tightening.
While the device shown in FIGS. 8 and 9 is in commercial use today, the device has limitations. First, the toothed anti-rotation device is limited to plastic bottle applications in which the backwardly facing teeth can grip and permanently indent the surface without fracturing the bottle. In glass bottles, the shock loading when the backwardly facing teeth grip the neck could result in bottle fracture. Second, although the forward and rearward converging surfaces 18, 19 are designed to be easily replaced, the replacement cost for each capper pocket approaches several hundred dollars and is relatively expensive. Third and most importantly, the device is functionally limited. Not all bottles have straight neck portions underneath the threads. Many bottle designs curve or taper the neck and when this occurs, the backwardly facing teeth make detrimental point contact with the bottle neck. More significantly, the diameter of the neck portions of plastic bottles, whether tapered or straight, typically vary from the nominal dimension anywhere from +0.025 inches to -0.020 inches producing an acceptable variation in neck diameters of as much as 0.045 inches. The dimensional variation means that for some bottles, the bottles neck will be cocked or wrenched into point indentation contact with the backwardly facing teeth as the cap is tightened. This will mark or score the neck wall and such marking is, of course, aggravated if the neck tapers and is not straight. Since the plastic used to manufacture the bottle is somewhat permeable, the scoring permits the gas of a carbonated beverage within the container to more easily permeate through the plastic contributing to a "flat" beverage. More critical, though, is that the neck marking or scoring acts as a stress riser to cause an occasional bottle failure. This is unacceptable. Additionally, the bottle is aesthetically marred.